Mimblewimble for LTC doesn't make it fungible

Elliptic’s solutions do not seek to trace or deanonymize confidential Litecoin transactions. Instead they allow businesses to identify whether a Litecoin transaction or wallet includes funds that have made use of this privacy feature. Compliance professionals can then use this information to assess risk and perform further due diligence.

So when you send your LTC via MW Side-Chain those LTC are not interchangeable with other LTC, because they are tainted and possibly won’t be accepted everywhere.

I would assume some LTC users who fiddle with MW are in for some bad surprises in the future.

It is unlikely that Grin users will have similar issues, since Grin won’t be accepted by “compliant” companies in the first place. So long term Grin would likely work as P2P transaction layer between people who are interested to use private lightweight Blockchain based transactions.

It’s a hot potato for companies.

Since Fiat Off Ramps will be hard to use, maybe users would just stick with Grin and use it mostly for transactions and not Gambling / Trading.
So moneyfloat could be: Fiat->Grin->Grin->Grin->Grin…